Science: Watery microbes fuel fresh fears over genetic release

Fresh doubts have been cast on the safety of releasing genetically engineered
organisms into the environment, following the discovery by biologists in
the US that microbes living in lakes, rivers and seas are capable of swapping
much more genetic material than expected. The fear is that the DNA introduced
into a microbe could migrate into other populations of microorganisms.

The new findings complicate current efforts to frame legislation governing
the release of genetically manipulated organisms (GMOs). A working group
of the UN Conference on Environment and Development met only last week to
work out draft international guidelines on the assessment and management
of risky procedures in biotechnology. If the draft is approved by the UN
secretariat in August, it will go forward for ratification to a major international
conference on the environment in Rio de Janeiro, Brazil, next year. It may
then form the blueprint for national laws governing releases of GMOs into
the environment.

Against this political backdrop, Tyler Kokjohn, of the Environmental
Research Division at the Argonne National Laboratory in Illinois, and colleagues
in other laboratories found that even when bacteria are at extremely low
concentrations, as they would typically be in water, they are still attacked
by viruses called bacteriophages (Journal of General Microbiology, vol 137,
p 661). Earlier studies suggested that below a certain threshold, the bacteria
are too far apart for the viruses to make the journey from one host to another.

This is a crucial finding because as bacteriophages reproduce inside
the bacterial cells they can introduce DNA from previous hosts into their
new host, a process called transduction. The DNA might be in the form of
a tiny loop called a plasmid, or other stretches of genetic material. When
the phages spread to new hosts, they take fragments of genetic material
with them which may be incorporated into the genome of the host bacterium.

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‘The prevailing wisdom,’ says Kokjohn, ‘was that transduction would
not be significant at these low concentrations. We have now shown that bacteriophages
are major effectors of transduction even at these low bacterial concentrations.’

Last year researchers discovered that bacteriophages are much more abundant
in water than previously thought. Lita Proctor, of the State University
of New York at Stony Brook, and Jed Fuhrman, of the University of California
at Los Angeles, showed that there were ‘enormous numbers of these particles,
and that many bacteria were infected and ready to split open, releasing
bursts of infectious phage particles’, says Kokjohn. ‘The potential of bacterial
viruses to control the genetic diversity of natural populations of their
hosts must be considered.’ This must be taken into account when evaluating
the potential risks associated with the release of genetically engineered
microorganisms into the environment. Kokjohn and his colleague are now investi
gating the fate of infected bacterial cells.